Vacuum pump



w. G. HOUSKEEPER June 16, 1925.

VACUUM PUMP Filed July 9, 1921 Patented June 16, 1925.

UNITED STATES FThihilf WILLIAM G. HOUSKEEPER, OF NEW YORK, N. L, ASSIG-NOR TO V ES'IERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

VACUUM PUMP.

Application filed July 9,,,1921,

To all whom it may concern:

Be it lmown that I, WILLIAM G. Hoosnnnrnn, a citizen of the United States of America, residin at New York, in the county of New ork, State of New York, have invented certain new and useful I mprovements in Vacuum Pumps, of which the following is a full, clear, concise, and exact description.

This invention relates to vacuum pumps and more especially to that type of vacuum pump in which metal vapor is used as the pumping medium.

In vacuum pum s of the metal vapor type, a supply 0 pumping medium is heated to cause the emanation therefrom of a vapor stream which acts mechanically upon gas from the vessel to be exhausted to drive it toward a roughing pump. Heretofore the heat for vaporizing the pumping medium has been generated exterior of the medium and then applied to the medium.

This inventionhas for its object to vaporize the pumping medium by heat generated within a supply of pumping medium.

To accomplish this object and to improve.

generally upon devices of this character, the pumping medium is placed in a crucible arranged within the pumping chamber and is sub ect to a high frequency electromag netic field. The eddy currents induced in the pumping medium heat it to the necessary temperature to cause the medium to volatilize.

This invention will be better understood by having reference to the following specification and accompanying drawing, wherein is disclosed a pump constructed in accordance with the invention.

A roughing pump 10, ca wide of reducing the pressure to 10 mm. o mercury 18 connected by means of the tubing 11 with the pum ing chamber 12, the lower end of whic comprises a bulb 13. A. tube 14 leads from the vessel 15 to be evacuated and enters the pumping chamber 12 at right angles thereto at a point above the bulb 13. Ar-

ranged in the bulb 13 is a crucible 16 of re fractory material such, for example, as lavite, in which is provided the pumping medium 17. The pumping medium is referably a metal such as lead, tin, bismut zinc or cadmium, each of which metals has, at

, room temperature, a vapor pressure less means of which the coil 18 Serial No. 483,472.

than the pressure employed within vacuum tubes of the pure electron discharge type, thus avoiding the need for a liquid air trap. Mercury, however, may be used as the pump ing medium in which case it will be necessaryto provide a liquid air trap in the tube 14.

The pumping medium is heated bymeans of heating current induced therein by an electromagnetic field produced by the coil 18 which surrounds the bulb 13. The coil together with the variable condensers 19 comprise an oscillation circuit. As a means for supplying exciting current to the oscil lation circuit, there is provided an electron discharge oscillator comprising the vacuum tube V, having the cathode F, the control electrode C and the anode A, the input and output circuits of which are connected with the oscillation circuit between the coil 18 and the condensers 19. Included in the output circuit of the oscillator is a generator G and a high fre uency choke coil 20. In the input circuit 0. the oscillator is provided a small resistance 21 to revent high frequency singing in said circuit and a grid leak resistance 22. In shunt with the resistance 22 is a lay-pass condenser 23 for alternating current in the input circuit. The connections of the input and output circuits of the oscillator to the oscillation circuit comprise stopping condensers 24: to prevent direct current flowing into the oscillation circuit. The cathode of the oscillator is grounded at 25, to protect both the input and output circuits ofthe oscillator against the accidental grounding of either of the circuits. Heating current is supplied to the cathode F by the battery 26.

This arrangement is capable of generating in the oscillation circuit, oscillations of an extremelydiigh order of frequency b roduces a high frequency electromagnetic eld. This field induces high frequency heating currents in the pumping medium 17 thereby generating heat sufiicient to vaporize the medium for the purpose specified.

The pumping chamber and a portion of the tube 14 are contained within the oven 27 whichmay be heated by the resistance units 28 supplied with current from the source 29. Tin lead and bismuth each has,

at its melting temperature, a-vapor pressure less than that employed in pure electron discharge devices. When any of these metals is used as the pumping medium, the oven is maintained at the melting point of the metal used. The vapor condenses on the wall of the pumping chamber 12 in liquid form and flows to the supply 17, thus makin the process continuous.

hat is claimed is:

1. The steps in the evacuation of a vessel which consist in producing a vapor stream by inducing eddy currents in a supply of pumping medium to heat said medium to its boiling point and directing said stream through a chamber communicating with the vessel to be evacuated.

2. The steps in the evacuation of a vessel which consist in producing a vapor stream by inducing eddy currents in a pumping medium to heat said medium to a boiling point, directing said vapor stream through a chamber communicatin with the vessel to be exhausted to entraln gases therefrom, and reducing the gas pressure in said chamber.

3. In combination, a pumping chamber, a supply of pumping medium therein, means for inducing eddy currents in the pumping medium, a connection between a vessel to be exhausted and the pumping chamber, and means for directing the vapor produced by the heating of said pumping medium across the mouth of said connection for entraining the gas in the vessel to be exhausted.

4. In combination, a pumping chamber, a supply of pumping medium therein, means for supplying high frequency currents for heating the pumping medium, a connection between a vessel to be exhausted and the pumping chamber, and means for directing the vapor produced by the heating of said pumping medium across the mouth of said connection for entraining the gas in the vessel to be exhausted.

5. In combination, a pumping chamber, a refractory crucible in said chamber, a supply of pumping material in said crucible, a coil surrounding said crucible, means for supplying high frequency currents to said coil for heating said pumping medium to produce a vapor, a connection between a vessel to be exhausted and said pumping chamber, and means for directing the taper pro duced by the heating of said pumping material across the mouth of said connection for entraining the gas in the vessel to be exhausted.

6. In combination, a crucible, a readily .vaporizable metal in said crucible, and means for inducing eddy currents in said metal to vaporize it.

In Witness whereof, I hereunto subscribe my name this 7th day of July, A. D. 1921.

WILLIAM G. HOUSKEEPEB. 

